2.3 After some discussion, the scientists decide that fertilization with Fe woul
ID: 801839 • Letter: 2
Question
2.3 After some discussion, the scientists decide that fertilization with Fe would be the most practical way to stimulate the uptake of 7.5 X 10^16 grams of C. They propose to fertilize the surface waters of the Southern Ocean over a wide area where studies have shown that production is Fe-limited. In the Southern Ocean, excess inorganic N is present in the surface waters at a concentration of about 20 /xM. What concentration of Fe should be added to the surface waters to stimulate the uptake of this much inorganic N, assuming that the C/N ratio in the phytoplankton equals the Redfield ratio of 106/16 by atoms? Assume that this much Fe is mixed into the euphotic zone, which is 50 m deep. Over what area of the ocean would the Fe additions have to be made? How does this figure compare to the surface area of the ocean, which is 3.6 X 10^8 km^2? Suppose that the area of the Southern Ocean the scientists plan to fertilize is about the size of Alaska, which has an area of 1.5 X 10^6 km^2. How many times would an area the size of Alaska have to be fertilized, as described above, to stimulate an uptake of 7.5 X 10^16 grams of C? Assume that a ship fertilizing the ocean with Fe can fertilize about 75 km^2 per day. How many ship-days would be required to fertilize an area the size of Alaska this many times?
Explanation / Answer
Answer:
As to fix 83000 kg of carbon dioxide, 1 kg of iron is required, therefore to fix 7.5 X 1016 gm (7500000kg) of C, we need 90.36 kg of iron.
The area effected by the concentration of iron is the euphotic zones, upto 50 m deep.
90360 gm/50* 10-3= 1807200 km2
The effected area is less than that the 3.6 X 108 km2
The area should be 0.834 times being fertilized.
The area is 165326.77 km2 being fertilized, therefore, 165326.77/75 = 2204 ships are needed.
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